A high precision knowledge of \(\beta \) -spectrum shape of particular isotopes is absolutely necessary for determination of the neutrino oscillation parameters in experiments with reactors and artificial neutrino sources.
The positive outcome of the LSND experiment [1]} obtained almost two decades ago, the calibration results of the radio-chemical Ga-Ge solar neutrino detectors [2]}, [3]} and the recent calculations of the reactor neutrino spectrum known as the “reactor anomaly” [4]}, [5]} have raised a question about existence of the sterile neutrino, which is mainly connected with the neutrino mass state shifted from the three known states by \(\delta m_{14}^2 \sim 1\)  eV and with effective mixing angle \(\sin ^2(2\theta _s) \sim 0.1\) .
In addition to the series of reactor and accelerator experiments looking for neutrino oscillations into the sterile state, there are projects employing artificial neutrino sources.
The most popular electron neutrino source is \(^{51}\) Ce isotope, proposed for use with various types of neutrino detectors and actually used for mentioned calibrations of SAGE and Gallex/GNO and BEST experiment [6]}.
